Occasional hard shifting
Occasional hard shifting Since my recent dyno tune (after cam install), my transmission has occasionally been shifting very hard. It seems to happen most after I have gotten on it but I am not sure that this is always the case. It has happened shortly after starting (fluid cold) and has also happened after driving (fluid hot). In either case, it continues shifting hard until I let it sit overnight and then it is back to normal.
My guess is that it is going into "limp" mode for some reason. Fluid level is good and I had it flush/exchanged a couple of weeks ago to no avail. The tranny went into this mode during the fluid exchange and the guys doing it said the idle pressure went from about 65psi to around 100psi.
The tranny seems to be otherwise functioning fine except for a slipping Y3000 converter clutch (also started at the dyno tune) - I have a new SS3400 on the way. Also, I do run a tranny cooler.
So, what causes the "limp" mode (if that is what this is) - I always thought it was excessive heat and/or low fluid but neither seem to be the case for me. How can I disable it?
Thanks,
Steve
My guess is that it is going into "limp" mode for some reason. Fluid level is good and I had it flush/exchanged a couple of weeks ago to no avail. The tranny went into this mode during the fluid exchange and the guys doing it said the idle pressure went from about 65psi to around 100psi.
The tranny seems to be otherwise functioning fine except for a slipping Y3000 converter clutch (also started at the dyno tune) - I have a new SS3400 on the way. Also, I do run a tranny cooler.
So, what causes the "limp" mode (if that is what this is) - I always thought it was excessive heat and/or low fluid but neither seem to be the case for me. How can I disable it?
Thanks,
Steve 
You will likely have a 1870 code as a result of the sliping converter clutch. this will cause maximum line pressure to be commanded on the 1-2 upshift. This is also a good way to "puke" the trans. Get that converter out of there. Get a PI Vigilanti if you do not want converter clutch problems.
Originally Posted by hellbents10
You will likely have a 1870 code as a result of the sliping converter clutch. this will cause maximum line pressure to be commanded on the 1-2 upshift. This is also a good way to "puke" the trans. Get that converter out of there. Get a PI Vigilanti if you do not want converter clutch problems.
Are you saying that replacing the converter might fix the hard shifting (i.e. high line pressure will no longer be commanded)? I hope so but, the hard shifting does not happen every time the converter slips. Is the command for high line pressure a tranny or computer function?
The hard shifting is noticeable on the 1-2 shift but it is worse going into gear from park/neutral due to my high idle (cam).
Thanks,
Steve What kinda cam you got? After talking to Dave at Rock-On, I'm pretty convinced that the bigger cams that cause map sensor problems (low vaccuum because of reversion) will also cause tranny line pressure problems. There are so many variables involved in calculating line pressure, and a cam just f's everything up. Save your trans and convert to vaccuum modulated. Eliminate the variables.
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Cam's a TR 227/224 on a 114 so it is not real radical.
I spoke to the tranny shop that is going to swap my converters and they also felt that the slipping converter clutch could be triggering the hard shifting and they were supprised that the 1870 code was not coming up. Maybe I had it deleted during programming changes I made a few years ago - I can't remember.
I am going to get the converter swapped early next week so we will see if that fixes the problem.
Thanks guys,
Steve
I spoke to the tranny shop that is going to swap my converters and they also felt that the slipping converter clutch could be triggering the hard shifting and they were supprised that the 1870 code was not coming up. Maybe I had it deleted during programming changes I made a few years ago - I can't remember.
I am going to get the converter swapped early next week so we will see if that fixes the problem.
Thanks guys,
Steve LS1 Tech Stories
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